These investigations are devoted to the development of non-invasive methods of accessing cellular structure and fucntion. Two general techniques are being used: Nuclear Magnectic Resonance (NMR) and optical spectroscopy. Over the last year we have developed and demonstrated the following NMR techniques: A two dimensional NMR technique was devised which permits the spectral editing of several metabolites simultaneously in the complicated proton spectrum in vivo. An on line blood flow method capable of use within the powerful magnetic field required for NMR experiments was developed and is now in routine use. A method of monitoring choline metabolism in vivo was developed using the stable NMR isotope deuterium labeled uniformly on the methyl groups of the compound. Using optical spectroscopy, a method of monitoring the topology of mitochondrial fluorescence in a single cardiac myocyte was developed as well as a method of monitoring and imaging the NADH fluorescence of the surface layers of the heart in vivo.